| Popis: |
The kinetics of adsorption and absorption of hydrogen and deuterium by ultra-high vacuum evaporated films of scandium, cerium, praseodymium, neodymium, samarium, gadolinium, dysprosium, holmium and erbium have been studied in the temperature range 78–400 K. Sticking probabilities have been measured using a flow technique and corrections have been made where necessary for desorption. The initial values of sticking probability are high, approaching 0.5– 0.7 for most metals, but are only around 10−3 in the case of samarium. S always decreases somewhat with initial uptake at the higher temperatures but may be, initially, relatively independent of uptake at 78 and 90 K. There is virtual equilibration between surface and bulk during absorption above 200 K at uptakes up to MH2; S values remain high throughout this region. At lower temperatures the surface saturates prior to the bulk and the redistribution of gas can be studied. The behaviour of hydrogen and deuterium is very similar in all aspects even at 78 and 90 K. Isosteric heats have been obtained in some cases. |
